The present invention relates to an electromagnetic converter such as a small generator, a motor and so on and to electronic equipment provided therewith, and the present invention is particularly applicable to a wrist watch and the like.
Conventionally, electronically-controlled mechanical timepieces hereinafter, referred to as electronically-controlled mechanical watches) are known which F, convert mechanical energy, which is generated by releasing a mainspring, into electric energy through an electromagnetic converter, control the value of a current flowing in the coil of the electromagnetic converter by actuating a rotation control means by the electric energy and display a time by driving hands fixed to a train wheel (Japanese Examined Patent Publication No. 7-119812 and Japanese Unexamined Patent Publication No. 8-50186, etc.).
Further, Japanese Unexamined Patent Publication No. 8-5758 proposes, in order to improve the efficiency for converting mechanical energy into electric energy, an arrangement using PC permalloy (hereinafter, referred to as, PC material) having a coercive force smaller than that of PB permalloy (hereinafter, referred to as PB material) so as to reduce the hysteresis loss of a stator and a coil core, which constitute the magnetic circuit of a generator in the electronically-controlled mechanical watches.
In contrast, recently proposed are electronic timepieces provided with generators (Japanese Examined Patent Publication No. 7-38029 and so on). The electronic timepiece is arranged such that the generator is assembled to a wrist watch main body. Electric energy necessary to drive the wrist watch is generated by the movement of an arm and accumulated in a capacitor and an electronic circuit is driven by the electric energy. In the wrist watch to which the generator is assembled, the power of a rotary movement weight is transmitted to the generator through a power transmission mechanism composed of a speed increasing train wheel, and electric power is generated by causing an electromagnetic inducing action on a coil due to the change of a magnetic field which is generated by the rotation of the rotor.
These generators comprise a rotor including a permanent magnet, a first yoke disposed around the rotor and a second rotor connected to the first yoke and including a coil. The second yoke is placed on the first yoke and the magnetic induction from the upper yoke to the lower yoke is secured through screws as shown in the drawings in Japanese Examined Patent Publication No. 7-38029.
The PC material, PB material and the like are ordinarily used as the material of the yokes of the magnetic converter.
In the electronic timepiece provided with the generator device, since the first yoke (stator) has no coil wound therearound, copper loss (electric resistance) is not increased by a wound coil. Thus, the PC material is used as the first yoke because it can increase a sectional area and accordingly it has magnetic flux density as small as 0.7 T and its iron loss is also small. In contrast, since the second yoke (coil core) has a coil wound therearound, when the sectional area thereof is increased, the length of a coil wire is increased and copper loss is increased thereby. Thus, the PB material is used in the second yoke because it has relatively high saturation magnetic flux density of 1.4 T, although it has iron loss larger than that of the PC material. That is, in the second yoke, the use of the PB material, which has large iron loss but can secure necessary magnetic flux even if the sectional area thereof is reduced, can decrease total loss as compared with the use of the PC material, which must increase the sectional area by which the copper loss of the winding thereof is increased, although its iron loss is low. Accordingly, the PB material is used in the second yoke.
In the electronic timepieces with the generators, when a speed increasing ratio achieved by the power transmission mechanism of an electromagnetic converter is set to about 100 in a generator, a rotor often operates at 50 to 150 Hz when the wrist watch is worn. As a result, iron loss is increased because an alternating-current magnetic field is generated to the yoke and an eddy current is generated to the material. Therefore, to develop an effective generator, a material having low iron loss is required in an alternating-current region (50-150 Hz).
When a secondary power supply such as a capacitor or the like is to be charged, a voltage effective at charging is obtained at a frequency of 50 Hz or more. Thus, a material having small iron loss in the alternating-current region is required also from this point of view.
Therefore, in the electronic timepieces provided with the generator devices, a material having small iron loss is required for the first yoke (stator) around which no coil is wounded. Whereas, a material having small iron loss and high saturation magnetic flux density is required for the second yoke (coil core) around which the coil is wound.
Further, the magnetic flux flowing in the magnetic circuit of the electronically-controlled mechanical watches is smaller by one order of magnitude as compared with that of the electronic timepieces provided with the generator devices and further the electronically-controlled mechanical watches have coil windings. Thus, even if the sectional area of the yoke of the electronic timepieces is reduced to decrease iron loss, the magnetization flux density is not saturated. Therefore, the PC material having the saturation magnetic flux density as small as 0.7 T is used in the electronic timepieces.
In the electronically-controlled mechanical watches, almost all the losses of the electromagnetic converter result from iron loss and the mechanical loss of gears and bearings (abbreviated as mechanical loss). A reason why the mechanical loss is caused by the speed increase near to 100,000 to 300,000 times, and further the mechanical loss has characteristics that it is proportional to iron loss. Therefore, reduction of iron loss is a subject for decreasing the total loss. In addition, the reduction of the iron loss is important because a duration time depends on the magnitude of the rotation load torque (magnetic torque) of the generator.
The present invention is an electromagnetic converter comprising a rotor arranged by including a permanent magnetic yoke disposed in the vicinity of the rotor for flowing magnetic flux and a coil disposed in the vicinity of the yoke, and the electromagnetic converter is characterized in that at least a portion of the yoke is composed of an amorphous metal magnetic material.
Further, the present invention is electronic equipment provided with the electromagnetic converter. The electronic equipment is preferably arranged, as portable type electronic equipment and most preferably arranged as, for example, a portable timepiece.
The electromagnetic converter includes a small generator, a motor and the like.
According to the present invention, the improvement of efficiency of a generator which is achieved by the reduction of iron loss can increase a duration time in the electronically-controlled mechanical watches and can reduce the size of a rotary movement weight in the electronic timepieces provided with generator devices, whereby the size and thickness of the timepieces can be reduced.
The yoke is ordinarily composed of magnetic members comprising at least two magnetic materials, and it is preferable that at least one of the magnetite members be composed of the amorphous metal magnetic material.
In the magnetic material, when magnetic flux flows, an anti-magnetic field is; produced in the direction of the flow and acts to prevent the flow of the magnetic flux. For example, when two flat-sheet-shaped magnetic materials are jointed to each other with the upper and lower surfaces thereof overlapped partially, a magnetization direction (direction in which magnetic flux flows) is the thickness direction of the magnetic materials. The intensity Hd of the anti-magnetic field is determined by the ratio of a plane surface area S to a sheet thickness T, which is represented by a formula Hd=k (S/T) (k: constant).
Therefore, in the amorphous metal magnetic material, when a thickness of a sheet is set to, for example, 25 xcexcm, since the sheet is thinner than the thickness 0.5 mm of a conventional material, for example, a PC material, the amorphous metal magnetic material is greatly affected by the anti-magnetic field and the magnetic flux is difficult to flow therein. As a the characteristics of the amorphous metal magnetic material are inferior to those of the PC material.
Thus, when at least two flat-sheet-shaped magnetic members composed of the above magnetic material are in contact with each other, if the sides thereof are approximately in contact with or jointed to each other as in the present invention (hereinafter, referred to as m contact with each other), the effect of the anti-magnetic field can be removed by flowing magnetic flux only in the lengthwise direction of the flat sheets.
Further, the addition of a joint member to at least one of the two magnetic members, which are in contact with each other and located on an upper side and a lower side, permits the magnetic flux to flow more easily.
When a magnetic circuit is arranged by coupling both the magnetic members to each other through the joint member, magnetic flux can be increased. Note that joint member need not be as thick as the magnetic members and it is sufficient for the thickness thereof to be half the thickness of the magnetic members. While it is preferable that the material of the joint member be a PC material which is difficult to be affected by the anti-magnetic field and the raw material thereof is available in a large thickness, it may be composed of an amorphous material (in particular, a Co type).
A specific example of the amorphous metal magnetic material is a Co amorphous metal.
The Co amorphous metal magnetic material contains Co in an amount of at least 50 wt %. It may contain Fe, Ni, B, Si and the like as other elements.
Further, a specific example of the amorphous metal magnetic material may be a Fe amorphous metal.
The Fe amorphous metal contains Fe in an amount of at least 50 wt %. It may contain B, Si and the like as other elements.
A specific example of the electronic equipment of the present invention is, for example, an electronically-controlled timepiece to which a small generator is assembled.
The electronically-controlled timepiece includes (1) an electronic timepiece provided with a generator device for generating power using a rotary movement weight, (2) an electronically-controlled mechanical watch, (3) a quartz watch driven by a step motor, and so forth.
Next, detailed description will be made as to the items (1) and (2).
First, the electronic timepiece provided with the generator device of the item (1) will be described.
The electronic timepiece is arranged by comprising at least a generator as the electromagnetic converter of the present invention, a storage means for storing the electromotive force of the generator, a timepiece circuit driven by the storage means, and a timepiece display unit driven by the timepiece circuit.
The generator of the electronic timepiece shown in the item (1) specifically comprises a rotary movement weight and a power transmission mechanism for transmitting the power of the rotary movement weight to the small generator.
The rotary movement weight generates mechanical energy.
The power transmission mechanism comprises a speed increasing train wheel having a plurality of combined gears.
The Co amorphous metal magnetic material is used for a first yoke (stator) in the generator of the electronic timepiece provided with the generator device, and the Fe amorphous metal magnetic material is used for a second yoke.
In the first yoke (stator), since no coil is wounded therearound, iron loss is not increased thereby. Thus, it is preferable to use the Co amorphous metal magnetic material in the first yoke (stator) because it can increase the cross sectional area of the first yoke, has low iron loss and low saturation magnetic flux density (0.7 T).
In contrast, in the second yoke (coil core), since a coil is wound therearound, when a cross sectional area is increased by the use of the Co amorphous metal magnetic material to prevent saturation, the length of a coil wire is increased, thereby increasing copper loss. Thus, reducing the cross-sectional area by the use of the Fe amorphous metal magnetic material, which has high saturation magnetic flux density (1.4 T) while the iron loss thereof is larger than that of the Co amorphous metal magnetic material, can reduce total loss rather than increasing copper loss by winding a coil around the Co amorphous metal magnetic material having a large cross sectional area. Therefore, it is preferable to use the Fe amorphous metal magnetic material.
Next, the electronically-controlled mechanical watch of the item (2) will be described.
The electronically-controlled mechanical watch shown in the item (2) is arranged by comprising, a main spring, a generator for converting the mechanical energy of the mainspring which is transmitted through a train wheel into electric energy, a time display hands coupled to the train wheel, a reference signal source such as a crystal oscillator or the like which is driven by the converted electric energy and a rotation control means driven by the converted electric energy similarly for controlling the rotation cycle of the generator. The yokes of the electronically-controlled mechanical watch are composed of the Co amorphous metal magnetic material.
In the electronically-controlled mechanical watch, since the magnetic flux flowing in a magnetic circuit is small and the watch is provided with a coil winding, no saturation is reached even if the cross sectional area of the yokes is reduced. This is a reason why a material having low iron loss such as the Co amorphous metal magnetic material is preferably used.
Specifically, the composition of the Co amorphous metal magnetic material is, for example, 66Co-4Fe-1Ni-14B-15Si.
Further, the composition of the Fe amorphous metal magnetic material is, for example, 78Fe-13B-9Si.
As shown in FIG. 1, in the measurement of the relationship between the magnetic torque (rotation load torque) of a rotor and the iron loss of a yoke, a decrease in iron loss reduces magnetic torque. Accordingly, the magnetic torque can be reduced by the use of an amorphous metal magnetic material having small iron loss. As a result, the rotation load torque necessary to drive the rotor of the generator can be reduced and the period of time during which the mainspring of the electronically-controlled mechanical watch is used (duration time) can be increased. Note that the reduction of the rotation load torque for driving the rotor of the generator also permits the reduction in size of, for example, the rotary movement weight and the generator in the electronic timepiece provided with the generator.
A generated voltage necessary to drive the IC of the electronically-controlled mechanical watch is at least 1 V. As can be seen from the following Table 1, to achieve this voltage, the torque required by a movement barrel which constitutes one gear of the train wheel by the gear in which the mainspring is accommodated is at least 30 gcm when the yokes are composed of the PC material and at least 20 gcm when the yokes are composed of the Co amorphous material. When torque is greater than the above value, the voltage of a capacitor in which the electromotive force of the generator is stored (the IC is driven by the output from the capacitor) is made to at least 1 V.
Preconditions: Obtained from an experiment in which a rotor frequency was set to 10 Hz and a speed increasing ration from a movement barrel to a rotor was set to 162,000.
A period of time from a time when a mainspring is fully wound to a time when it is rewound, that is, a duration time can be determined by (speed increasing ratioxc3x97number of turns of mainspring)÷(rotor frequencyxc3x9760xc3x9760 hours). Specifically, as shown in Table 1, when the yokes are composed of the PC material and a timepiece employs a train wheel having a speed increasing ratio of 162,000, if the number of turns of the mainspring which is effective to the duration time is about 5.3 turns, a calculated duration time is 24 hours. When the yokes of the generator is composed of an amorphous material, if the yokes are used by increasing the speed increasing ratio to 1.5 times the above speed increasing ratio, that is, to 243,000 in correspondence to the reduction of the power generation torque to {fraction (1/1.5)} (since the rotational speed of the rotor is constant, the rotational speed of the movement barrel is reduced to {fraction (1/1.5)}), the duration time of 1.5 times the above duration time, that is, 36 hours can be achieved in the same effective number of turns (5.3 turns).
In contrast, in the electronic timepiece provided with the generator device., the rotary movement weight by which driving power is generated from the generator can be easily moved because the aforesaid magnetic torque is reduced.